The present invention relates generally to motion control systems, and, more particularly, to a method and apparatus for sizing a power processing device serving multiple drive units.
Motion control systems such as those employed in industrial environments typically require power from one or more power sources, in the form of primary and/or auxiliary power. Not uncommonly, different types or levels of power (e.g., DC or AC power), or powers having multiple different characteristics (e.g., different voltage levels, current levels, etc.) are required.
Typically, the power that is provided to the motion control systems is received from one or more power lines (e.g., a utility grid) and then converted into the desired forms of power. However, in certain embodiments, power can be received from power sources other than power lines, such as local power generation sources (e.g., local generators or batteries).
To provide the required forms of primary, control, and/or auxiliary power to the motion control systems based upon the received power, many different front-end circuit components are often required. These front-end circuit components not only can provide power conversion, but also can serve other purposes as well, for example, circuit protection to protect against power spikes. For example, the National Electric Code requires that branch circuit protection be provided in connection with the delivery of power to motor controllers/motor drivers.
Among the many different circuit components that can be utilized in any given system are power conversion components, switching components, such as contactors, protective components, such as circuit breakers and fuses, filtering components, and even additional power sources. Power processing circuitry may be implemented on an “ad hoc” basis when motion control systems are installed or specialized power processing devices may be implemented.
One factor that influences the complexity and cost of a power processing circuit or device is the current required to supply the served drive units. Some drive units may serve only a single axis machine, while other drive units may serve multiples axes. Typically, the power processing device is sized based on the maximum current ratings for the served drive units. The number of drive units that a particular power processing device can serve is thus limited by the sum of the maximum current ratings.
In actual operation, the current requirements for a given drive unit are typically much less than the rated current. Using rated current to size the power processing device reduces the number of drive units that be served by each power processing device, thereby increasing the number or rating of the installed power processing device, which increases the cost and complexity of the motor control system. Therefore, there is a need for a technique to size power processing devices serving one or more drive units that incorporates the actual demand requirements of the drive units.
This section of this document is intended to introduce various aspects of art that may be related to various aspects of the present invention described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.